The invention concerns a bending apparatus for long workpieces, especially tubes, and a device for measuring tube bend length.
In the heating field, it is known that bending apparatuses are applied to the bending of tubes, pipes, and the like (hereinafter, referred to as “tubes”). The tubes are frequently bent at right angles. For this service, a known, generic bending apparatus possesses a bending segment carrying a semicircular, protractor-like scale. The scaled bending segment pivots by means of a drive motor and the bending apparatus includes a fixed bending counterpart to hold the tube against the said bending segment. Such a bending apparatus has been disclosed in DE 195 10 330 C2. The bending apparatus includes a profiled press-fit carrier which seizes the free end of the tube and rotates the tube so that the tube is then curved in conformity with a circular arc of the bending segment.
The tube center bend point is advantageously placed by the operator at a predetermined and desired location on the tube. In doing this, it is known, that the operator marks off a longitudinal distance from a selected reference point on the tube. The marked distance is to coincide with tube bend lengths to be defined on an unbent tube and should exactly align with a central axis of the tube following bending, governed by the markings of the above procedure.
Subsequently, a point for the start of bending is defined, by again measuring from the reference position on the extending workpiece. This bend start point linearly differs from the bend center point by a length needed for compensation. The bend start-point of the tube is positioned at the angular zero degrees graduation as seen on a protractor scale on a bending segment and the bending procedure then takes place from this position.
In the cited known determination of the above starting bend point for the bending, the determination is carried out in a somewhat complex manner, either by empirical judgment based on trial and error, or by reference to tabulated data, in which information regarding curvature compensation lengths for currently involved tube diameters in accord with corresponding radii of bends is set forth. The so determined compensation length can then be added to (or subtracted from) a predetermined specified straight line length as measured from the established start-point.
The purpose of the present invention is to provide a bending apparatus for tubes which advantageously includes a bend-length selector which automatically marks a start point for a bend at a predetermined longitudinal position on the tubes.